State-of-the art in assessing passivation condition of stainless steels

Nehrđajući čelici svoju korozijsku otpornost duguju stvaranju zaštitnog pasivnog sloja oksida na površini. U radu je dan pregled niza metoda kojima se ispituje pasivno stanje nehrđajućih čelika. ASTM standardi A967 i A380 nude metode poput testa uranjanja u vodu i feroksil testa koji samo kao prolaz/pad testovi utvrđuju nalazi li se nehrđajući čelik u pasivnom stanju. Na tržištu se pronalaze i uređaji dizajnirani za ispitivanje postojanja pasivnog stanja. Tehnike analize površine XPS i AES daju uvid u kemijski sastav pasivnog sloja i omjere koncentracija pojedinačnih prisutnih oksida. Elektrokemijska mjerenja CPDP i EIS daju informacije o mjeri otpornosti nehrđajućeg čelika na pojavu korozije. U radu su prikazana i neka novije provedena istraživanja te metode novijeg vremena koje su često sinkrotron bazirane tehnike i mikroskopije skenirajućom sondom poput sinkrotron bazirane XRR i SKP. Daljnja napredovanja u području ispitivanja pasivnog stanja nehrđajućeg čelika potrebna su i korisna posebno u svrhu dobivanja saznanja koja će se upotrijebiti za prevenciju korozije.Stainless steels are corrosion resistant due to formation of a protective passive oxide layer on their surface. This study provides an overview of a number of methods used to assess the passive state of stainless steels. ASTM standards A967 and A380 offer methods such as the water immersion test and the ferroxyl test that are pass/fall tests which determine whether stainless steel is in a passive state. On the market, there are stainless steel passivation testers designed to verify the existence of a passive state. Surface analysis techniques, XPS and AES provide insight into the chemical composition of the passive layer and the concentration ratios of the present oxides Electrochemical CPDP and EIS measurements provide information on a stainless steel's resistance to corrosion. This study also presents some more recently conducted research and recent methods, which are often synchrotron-based techniques and scanning probe microscopies, such as synchrotron-based XRR and SKP. Further advances in the field of testing passive state of stainless steels are necessary and useful especially for the purpose of obtaining knowledge to be used for corrosion prevention